This invention relates to an electrical switch assembly such as a single-pole, double-throw electrical switch, and more particularly to an improved construction of a rocker type switch assembly configured without a center contact.
A known rocker-type electrical switch assembly, such as a single pole double throw (SPDT) switch assembly, typically includes a housing having first and second stationary contacts mounted on opposite sides of an interior cavity. A stationary “center” contact is centrally located between the stationary first and second contacts. In the prior art, the center contact is channel-shaped and interconnected with a prong that extends from the bottom portion of the housing.
A V-shaped movable contact member or rocker formed of an electrically conductive material is engaged with and pivotable about the channel-shaped center contact. The V-shaped movable contact member includes a first leg and a second leg that are operable to selectively connect the center contact to either the first stationary contact or the second stationary contact in response to manual operation of an actuator movably mounted to the housing. Each leg of the V-shaped movable contact member carries a button-type contact that establishes contact with the underlying first or second stationary contacts. Upon the contact member establishing contact, a circuit path is completed from the respective first or second stationary contact and associated prong, through the V-shaped contact member, to the center contact, and on to the interconnected prong. The rocker type switch assembly can be used as a transfer switch assembly to selectively connect an electrical load between one of two separate power supplies, or as a switch assembly to selectively connect a power supply to one of two separate electrical loads.
FIG. 11 illustrates a center contact arrangement known in the art. The arrangement includes an electrically conductive U-shaped or channel shaped center contact 14 connected to a shaft 15 and a prong 16. The center contact 14 is configured to pivotally support a V-shaped contact member 17 having a number of button-type contacts at its ends.
When in an inoperative or OFF position, the V-shaped contact member 17 is positioned such that the button-type contacts are out of contact with a first 18 and a second stationary contact 19. The V-shaped contact member 17 remains in contact and is supported by the center contact 14. To place the switch in a first ON position, a plunger type actuator is pivoted relative to the switch housing to cause the V-shaped contact member 17 to rock or pivot on one of the walls of the center contact 14. One of the arms of the contact member 17 moves downwardly into engagement with underlying stationary contact 18, completing an electrical path from the stationary contact 18 through the contact member 17 to the center contact 14. When returned to the OFF position, the V-shaped contact member 17 pivots on the wall of the center contact 14, disengaging the contact member 17 from the stationary contact 18.
The center contact arrangement works in a similar fashion with respect to a second ON position, in which the other leg of the V-shaped contact member 17 establishes contact with the respective second contact 19, completing an electrical path from the second contact 19 through the contact member 17 to the center contact 14.
The known rocker-type transfer switch assembly has several drawbacks. For example, the first and the second contacts are located in close proximity to the center contact channel. Because of this proximity, arcing or short circuiting is possible when the first and second contacts are connected to separate electrical inputs. Furthermore, the configuration of the center contact area is cumbersome and inefficient to assemble.